ABSTRACT
The experiment was carried out with the objective of evaluating the gross margin, the productive and reproductive performance of beef heifers kept exclusively on ryegrass pasture (Lolium multiflorum Lam.) or ryegrass receiving 0.5 and 1.0% of body weight (BW) of whole rice bran as supplement. The grazing method was the rotational and the interval between grazings was set by the thermal sum required for the appearing of 1.5 ryegrass leaf (187.5ºC). The experimental design was completely randomized with repeated measures. Heifers average daily gain did not differ between the feeding systems. The stocking rate and weight gain per area were higher when heifers received 1.0% BW of whole rice bran. The higher gross margin was observed when heifers received 0.5% BW. The variable cost obtained for the different feeding systems showed increasing behavior depending on the WRB levels, surpassing the exclusive use of ryegrass in 49.4% and 81.8%. The final body weight, body condition score and reproductive tract score did not differ between the feeding systems. Considering an adult animal with an average body weight of 450kg, the heifers at the beginning of the experiment showed 34% of mature body weight and final average body weight of 56% of adult weight. The use of rice bran levels (FAZ) in the rearing of beef heifers under rotational grazing on ryegrass does not change the average daily gain and the reproductive tract score. The supply of 1% FAI showed substitutive effect, providing an increase in capacity of 31,2% and 38.3% rate of the gain per area. The food system AZ0,5 allowed a higher gross margin, as the economic return was positive in all food systems, with better return calculated for the exclusive use of ryegrass.
Keywords:
weight gain per area; Lolium multiflorum Lam. Gross margin; supplement; stocking rate